Effect of pyruvate and HEPES on pulmonary allograft acidosis and cell death after long-term storage

Abstract Introduction: Perfadex® has become a preferred lung preservation solution. We previously demonstrated that adding pyruvate to Perfadex® increases graft metabolism and improves reperfusion lung function after 24 hours of storage. However, increased metabolism can lead to greater acidosis, risking additional cellular injury. We hypothesized that more effective pH regulation would result in further improvements in lung survival after extended hypothermic storage. Methods: Rat lungs (n = 6 per group) were harvested and stored for 24 hours at 10 C in one of three storage solutions (initial pH 7.4 ± 0.1): 1) Perfadex® group, 2) Perfadex® with 32mM Pyruvate added (Pyruvate group) 3) Perfadex with Pyruvate and 30mM N-2-hydroxyethylpiperazine-propanesulfonic acid (HEPES group). Control lungs were removed and immediately fixed. pH change in the storage solution was measured after 24 hours. Cell death was evaluated by quantifying apoptotic (TUNEL positive) and necrotic (trypan blue permeable) cells in tissue sections. Results: Cell death in control lungs was minimal. Lungs stored in Perfadex® demonstrated the greatest degree of cell death. Lungs from the Pyruvate group exhibited decreased cell death despite much greater acidosis. The HEPES group demonstrated improved acid/base balance and significantly reduced graft cell death compared to Perfadex® and Pyruvate groups (p Conclusions: Adding pyruvate to the preservation solution increases acid formation during storage but reduces cell death. HEPES ameliorates this acidosis and significantly reduces allograft cell destruction. Further refinements to create a more physiologic storage milieu may prove important for long-term lung preservation. Table 1Cell death and pH changes in stored allograftsGroupΔ pH% Dead cells% Apoptotic% NecroticControlNA1 ± 1∗17 ± 983 ± 9Perfadex−0.42 ± .02∗25 ± 4∗2 ± 298 ± 2Pyruvate−0.53 ± .03 # 15 ± 2 # 1 ± 199 ± 1HEPES−0.15 ± .02 † 8 ± 1 † 6 ± 494 ± 4Data are mean ± SEM; comparisons by one-way analysis of variance.∗p